Process for treating molten ferrous metal



United States Patent 3,151,975 PROCESS FOR TREATING MOLTEN FERROUS METALJulius D. Madaras, Rockwall Place, Longview, Tex. No Drawing. Filed May4, 1960, Ser. No. 26,696 3 Claims. (Cl. 7548) My invention is a newmethod for refining iron and steel, for carburizing iron, and for addingadditives to iron to form nodular iron.

For refining molten iron and steel a mixture of lime and alumina isprepared and, if so desired, preheated to a temperature below the slagformation. This mixture may be in any desired form, pellets, briquettes,rods, porous or densely compressed. When these are poured or placed overthe top of molten metal contained in a ladle or vessel, hot lumpy carbonsuch as charcoal, loose or in briquette form, is placed over the wholecharge and the carbon layer is then pressed down into the metal by asuitable plunger. The pressure on the plunger is then released, thecarbon lifts and is again pressed into the molten bath. This operationis repeated for any desired number of times until the desired reactionis completed.

These lumps of lime and alumina may also be placed into the empty ladle,preferably on a layer of carbon, then covered by hot carbon. This carbonpile is held down by a plunger or by any other suitable means and molteniron is poured into the ladle. The molten iron heats the lumps, formingmolten slag which rises to the top through the molten iron and at thesame time refines the molten iron. The pressure on the carbon pile isreleased several times and the carbon pressed down into the molten metalbath in order to make the mixing of the slag and iron and thereby therefining more complete.

High carburization may also be accomplished by repeated plunging of thecarbon pile into the iron bath.

The lumps of lime and alumina may contain other slag forming elements asdesired. It may also contain carbon which will facilitate the furthercarburization of the molten iron.

My method will also be useful for putting into the metal bath alloyslighter than the metals themselves. For instance, by my method magnesiummetal can be added easily and economically to the iron for alloying thetwo metals. Lumps or bars or sheets of magnesium are placed on thebottom of the furnace and hot carbon lumps are placed over the solidmagnesium and the carbon pile is held down as previously described. Themolten iron melts the magnesium, absorbs it and becomes alloyed with it.In this way the oxidation of most of the magnesium is prevented,practically all the magnesium is absorbed and the amount is controlled,except for the amount which combines with the oxygen contained in themolten iron. The hot carbon maintains a reducing atmosphere so thatthere will not be much tendency for oxidizing the magnesium.

If absorption of carbon is not desired, some very dense carbon such asbroken electrodes or possibly dense refractories may be utilized.

The solid magnesium can also be held down at the bottom of the furnaceby the plunger, a solid carbon rod, column or electrode which preferablyhas a hollow space at the bottom, while the molten metal is poured intothe furnace. The magnesium will be prevented from floating to the topand therefore from becoming oxidized. The molten metal then willdissolve and absorb the magnesium, part of which will also act todeoxidize the molten metal. The additive can be attached to a suitablerod of steel and be thrust into the bath to be absorbed.

It should be kept in mind that, while for the sake of simplicity andbrevity only magnesium as light metal has been mentioned, neverthelessall other nodulizing metals or their mixtures, such as calcium, barium,titanium, cesium, etc., may be used, or even heavy metals or anycombination thereof may be used without departing from my invention.

Another but similar method of carburizing the metal and at the same timeputting in the deoxidizing light metal or other alloys is as follows:

Finely divided or granular carbon and finely divided or granular metalor metals are mixed and made into briquettes, rods or any other suitableform. If desirable, a suitable hinder or other materials such as lime,alumina, etc., may be also mixed in. This mixture may also be coatedwith suitable coating like tar or clay, or may be enclosed into metalliccasing to prevent slow oxidization or even possible ignition. Thebriquettes may have any desired looseness and porosity, or the mixturemay even be kept in a loose state when surrounded by a casing orcoating. These briquettes will then be submerged into the furnace asdescribed above. Since the molten iron has a great afiinity for themagnesium and other similar elements mentioned above, it will absorb themagnesium, leaving the carbon very porous and thereby facilitating theabsorption of carbon also.

A combination of slag forming refractories such as alumina, silica andlime may also be so mixed with carbon that they react with each other inthe molten iron and form slag. The carbon mixed with them is absorbed bythe metal to provide the proper carburization or to add the balance ofcarbon desired. Preferably, mainly alumina and lime should be used asslag forming materials. At the same time the slag forming materials arereacting to form slag, they develop a large amount of heat helping notonly the carburization but also, if desired, the temperature rise of themolten metal as well as the refining of the metal.

This, for instance, will be very important when making iron or steelwith nodular structure, the so-called nodular iron. In the nodular ironthe very low sulphur content is very important. The hot slag formationwhich will cause boiling and agitation of the molten metal will havegreat afiinity for the sulphur, especially if so proportioned that it isstrongly on the basic side. It is also partly due to the hightemperature developed.

If it is desired to raise the temperature of the molten iron, afterreleasing the pressure on the carbon, air at any temperature or oxygenor enriched air may be blown into it in order to raise the temperatureof the carbon by the resulting combustion. After that the hot carbon ispulverized into the metal to raise its temperature.

This application is a continuation-in-part of my application Serial No.454,102, filed September 3, 1954, and now abandoned, which in turn is acontinuation-in-part of my application Serial No. 125,934, filedNovember 7, 1949, now Patent No. 2,688,535, dated September 7, 1954.

What I claim as my invention is:

1. Metallurgical process which comprises placing solid metal havingnodulizing properties in a container, covering the metal layer withcarbon, and pouring molten ferrous metal into the container whilemaintaining the metal submerged until it melts and nodulizes the iron.

2. Metallurgical process which comprises placing solid magnesium metalin a container, covering the metal layer with carbon, and pouring moltenferrous metal into the container while maintaining the magnesium metalsubmerged until it melts and nodulizes the iron.

3. Metallurgical process which comprises placing a solid metal of theclass consisting of magnesium, calcium, barium, titanium and cesium in acontainer, covering the metal layer with carbon, and pouring moltenferrous metal into the container while maintaining the metal submergeduntil it melts and nodulizes the iron.

(References on following page) 0 References Cited in the file of thispatent UNITED STATES PATENTS Koneman Sept. 29, 1903 Pacz Aug. 24, 1926Moore Nov. 28, 1933 Priestly May 9, 1939 Perrin June 4, 1940 H012 Mar.18, 1947 FOREIGN PATENTS Great Britain 1876

1. METALLURGICAL PROCESS WHICH COMPRISES PLACING SOLID METAL HAVINGNODULIZING PROPERTIES IN A CONTAINER, COVERING THE METAL LAYER WITHCARBON, AND POURING MOLTEN FERROUS METAL INTO THE CONTAINER WHILEMAINTAINING THE METAL SUBMERGED UNTIL IT MELTS AND NODULIZES THE IRON.